1. Field of the Invention
The present invention relates to a method and apparatus for treating a waste substance using a thermit reaction, and more particularly to a method and apparatus for processing waste substance, for instance, toxic compounds used in chemical weapons and industrial wastes including incineration ash so as to make the waste substance harmless and reusable.
2. Prior Art
In light of the adoption of the Chemical Weapons Convention which concerns prohibition on the use of chemical weapons, etc., the establishment of techniques for rendering harmless the toxic compounds used in chemical weapons has become an urgent matter.
The toxic compounds used in chemical weapons should be understood in their broadest meaning so as to include various types of gas warfare agents. Gas warfare agents as the toxic compounds used in chemical weapons are those defined as follows ("Kagaku Daijiten" (Chemical encyclopedia), Kagaku Daijiten Henshuiinkai, ed., Kyoritsu Shuppan K.K., published Mar. 15, 1984). Specifically, gas warfare agents are: liquid or solid compounds having poisonous properties that can be formed into a gas or fumes; and substances which injure the functions of the living body generally or locally, and which are used in warfare for the purpose of injuring the enemy.
Nekrascov's theory is known with regard to the relation of the structure of toxic compounds that constitute the gas warfare agents and their toxicity. The toxic compounds used in chemical weapons referred to in the present invention should be understood to include all compounds indicated by the rule of thumb described below in which Nekrascov's theory is applied to gas warfare agents.
From Nekrascov's theory (rule of thumb applied to gas warfare agents), the structures of gas warfare agents can be classified as follows:
(1) Halogenated esters. e.g.: methyl chloroformate, phosgene (COCl.sub.2), diphosgene. PA1 (2) Halogenated ethers and thioethers. e.g.: dichlordimethyl ether, ypperite (mustard gas, dichlordiethyl sulfide) [(CH.sub.2 ClCH.sub.2).sub.2 S]. PA1 (3) Halogenated ketones. e.g.: chloracetone, bromacetone. PA1 (4) Aromatic compounds having halogens on side chains. e.g.: benzyl chloride, benzyl iodide. PA1 (5) Halogenated nitro compounds. e.g.: dichlorpicrin. PA1 (6) Cyanogen compounds. e.g., cyanogen chloride, bromobenzyl cyanide. PA1 (7) Arsenic compounds. e.g., lewisite (ClCH=CHAsCl.sub.2), chlordiphenylarsine, ad,nsite. PA1 (8) Organic phosphate compounds.
According to the Nekrascov's theory, substances having a toxic action are constituted as having foxophores within their molecules and having an auxotox that characterizes the toxic action of the foxophore. Examples of the foxophores include the following: --C(.dbd.O)--, --S--, --C.dbd.C--, --N(O.sub.2), --N.dbd.C, --As--, etc. Examples of the auxotoxes include the following: halogens, oxygen atoms, amino groups, benzyl groups, phenyl groups, methyl groups, ethyl groups, etc.
In the past, several methods have been known and used for rendering harmless toxic compounds used in chemical weapons, for example, the specified gas warfare agents such as yperite (mustard gas) and lewisite.
For example, methods that have been proposed and put into practice are: to induce the decomposition of the toxic compound used in chemical weapons in a high temperature combustion region by creating a high-temperature atmosphere of 1400.degree. C. or above by the combustion of a fuel; to induce the decomposition of the toxic compounds used in chemical weapons by means of a substance (such as silver) that is activated by ultraviolet irradiation in a solution system; and to induce the decomposition of the toxic compounds used in chemical weapons by means of a molten metal.
However, the above decomposition methods for toxic compounds used in chemical weapons have various defects. In order to create a closed system for rendering materials completely harmless, the decomposition device is large. The decomposition treatment capacity is too small, and the methods are extremely inefficient for the treatment of the vast quantities of compounds used in chemical weapons that have been used in the past and are presently stored. The treatment not only of toxic compounds extracted and removed from chemical weapons but also toxic compounds that occlude or impregnate the warhead materials of chemical weapons, as well as the surrounding soil into which toxic compounds have leaked from the warhead materials of chemical weapons and which are contaminated with the toxic compounds (hereinafter referred to simply as surrounding soil), etc., is extremely difficult or impossible.
On the other hand, melting-treatment techniques that use thermit reactions have been known as methods in the volume reduction treatment of waste products such as industrial waste products and household garbage as disclosed in, for example, Japanese Patent Application Laid-Open (Kokai) Nos. H9-60844 and H7-331354.
In the techniques disclosed in Japanese Patent Application Laid-Open (Kokai) Nos. H9-60844 and H7-331354, incineration ash or the like is melted into slag using the large quantity of heat (super-high heat) produced by oxidizing aluminum, thus reducing the volume of the waste product and sealing the heavy metals and dioxins contained in the waste product in the slag, making them harmless. Such a slag is then used as, for instance, concrete aggregate, thus being made into a renewable resource.
This method is considered to be superior to those treatment methods previously used such as electric melting furnaces, burner melting furnaces, plasma melting furnaces and the like in terms of conservation of energy costs relating to electric power, file, etc., the scale of the facility, and reduction of equipment costs.
Nevertheless, in conventional self-sustaining type melt treatment using thermit reaction heat, problems have occurred such as unevenness of the thermit reaction, producing heat generation failure or interruption of heat generation due to fluctuations in the blend ratio or blended state or of the material properties of the thermit reaction agent (or merely thermit agent) and the material to be treated such as incineration ash.